The development of an axial active magnetic bearing

Abstract

In this dissertation, the author presents the operation and development of active magnetic bearings (AMBs) , with specific focus on axial AMBs . The project objective is the development of an axial AMB system. The electromagnetic design, inductive sensor design, dSpace controller model design and actuating amplifier design are aspects discussed in this dissertation. The physical model constitutes two electromagnets positioned above and beneath a 2 kg steel disc with an air gap of 3 mm on either side of the disc. The electromagnetic design is done analytically and verified using Quickfield finite element analysis software. Inductive sensors are designed to obtain position feedback from the model. These sensors measure the distance of the air gap between the suspended steel disc and the electromagnets. The dSpace 1104 controller board and software is used for controlling purposes. This dissertation describes the system development from the Simulink model to the real-time model, where the dSpace controller board controls the physical hardware. The dSpace controller sends out control signals via DIA ports to actuating amplifiers. The actuating amplifiers then provide a controlling current to the electromagnets. The steel disc is attracted or released according to the signal provided. The inductive position sensors provide feedback from the model via the AID port of the dSpace controller to close the control loop. The control performance of the model is evaluated through steady state analysis (static load test), dynamic disturbance analysis (downward disturbance test) and step response analyses (amplitude step response test). The step response analysis provide information about the time-to-peak, settling time, percentage overshoot, natural frequency, damping ratio, damping constant and stiffness of the model. The experimental results obtained agree with the expected theoretical norms. Future possible projects can be done on the improvement of the sensor (designing a sensor-less sensor), designing advanced control techniques for the axial AMB model by using the dSpace DS 1 104 controller and designing an axial AMB model for high speed applications.